A mechanical seal comprises a “floating” component which is mounted to be axially movable around the rotary shaft of, for example, a pump, and a “static” component which is axially fixed, typically being secured to a housing. The floating component has a flat annular end face, i.e. its seal face, directed towards a complementary seal face of the static component. The floating component is urged towards the static component to close the seal faces together to form a sliding face seal, usually by means of one or more spring members. In use, one of the floating and static components rotates; this component is therefore referred to as the rotary component. The other of the floating and static components does not rotate and is referred to as the stationary component.
Those seals whose floating component is rotary are described as rotary seals. If the floating component is stationary, the seal is referred to as a stationary seal.
If the sliding seal between the rotary and stationary components are assembled and pre-set prior to despatch from the mechanical seal manufacturing premises, the industry terminology for this is “cartridge seal”. If the rotary and stationary components are despatched individually (unassembled) from the mechanical seal manufacturing premises, the industry terminology for this is “component seal”.
Mechanical seals are used in all types of industries to seal a variety of different process media and operating conditions. The general industry term which defines the area adjacent to the process media is “inboard”. The industry term which defines the area adjacent to the atmospheric side is “outboard”.
With the exception of the mechanical seal faces, the most costly item of a cartridge mechanical seal is the gland plate. The raw material for a gland plate is typically either cast metal or a solid metal bar. Alternative materials such as plastic are also occasionally used. Subsequent machining operations on the gland plate raw material are required in order to accurately fit the mating components.
For most types of mechanical seals, typically, one seal gland is employed for each size of seal in both single and double seal formats. With over 30 standard seal sizes, in any given product range and at least two gland formats, a company's gland plate inventory costs can be considerable. Furthermore gland production costs are high due to the number of manufacturing operations required to process a given gland.
There is a need for a seal gland which is of relatively low cost including the use of material which, after the original manufacturing operation, requires no subsequent machining such as turning, milling or drilling.